Compounds derived from the Chinese medicinal plant Tripterygium wilfordii (TW) have been identified as having useful therapeutic properties, particularly immunosuppressive activity and anticancer activity. These compounds include triptolide, tripdiolide and 16-hydroxy triptolide. Synthetic derivatives and prodrugs of these compounds have also shown therapeutic activity, often in combination with improved pharmacological properties. See, for example, U.S. Pat. No. 5,468,772 (Tripterinin compound and method), U.S. Pat. No. 5,648,376 (Immunosuppressant diterpene compound), U.S. Pat. No. 5,663,335 (Immunosuppressive compounds and methods), U.S. Pat. No. 5,759,550 (Method for suppressing xenograft rejection), U.S. Pat. No. 5,843,452 (Immunotherapy composition and method), U.S. Pat. No. 5,962,516 (Immunosuppressive compounds and methods), U.S. Pat. No. 6,150,539 (Triptolide prodrugs having high aqueous solubility), U.S. Pat. No. 6,294,546 (Uses of diterpenoid triepoxides as an antiproliferative agent), U.S. Pat. No. 6,537,984 (Uses of diterpenoid triepoxides as an antiproliferative agent), U.S. Pat. No. 6,548,537 (Triptolide prodrugs having high aqueous solubility), U.S. Pat. No. 6,569,893 (Amino acid derivatives of triptolide compounds as immune modulators and anticancer agents), U.S. Pat. No. 6,599,499 (Uses of diterpenoid triepoxides as an antiproliferative agent), and U.S. Pat. No. 6,620,843 (Anticancer treatment using triptolide prodrugs), each of which is incorporated herein by reference.
Isolation of the native compounds from the plant material has, to date, typically required laborious extraction and purification procedures. Kupchan et al. (1972, 1977) describe a method in which the root material is extracted with ethanol, the solid extract is dissolved in ethyl acetate and partitioned with water, and the ethyl acetate fraction is chromatographed on silica gel. Cheng et al. (1993) describe a method in which the first extraction employs hot water, followed by addition of ethanol, filtration, removal of the ethanol, partitioning with chloroform, and chromatography on silica gel. The method described by Lipsky et al. (1996) employs subsequent extractions with chloroform, methanol, and toluene, with removal of solvent between each extraction, followed by chromatography on alumina and then on silica gel. Wiedmann et al. (1998) describe a method in which the root material is extracted with refluxing aqueous ethanol, the solid extract is partitioned between dichloromethane and water, and the dichloromethane phase is concentrated and chromatographed on silica gel. Ken et al. (2004) describe a method in which the root is extracted repeatedly with ethanol, and the extracts are concentrated and extracted repeatedly with chloroform, followed by chromatographic purification.
In isolation methods to date, the extraction steps generally produce an extract which retains large quantities of undesired materials, which then must be removed chromatographically, requiring large investments of time and materials. In view of the therapeutic utility of these compounds, higher efficiency methods for isolation and purification are desired.